A 3GPP that establishes a technology standard of a 3rd generation mobile communication system has started a research into long term evolution/system architecture evolution (LTE/SAE) technology as part of an effort to optimize and improve performance of 3 GPP technologies from the end of 2004 in order to cope with various forums and new technologies associated with 4th generation mobile communication.
SAE that is progressed around 3GPP SA WG2 is a research into network technology to determine a structure of a network with an LTE work of a 3GPP TSG RAN and support mobility between model networks and one of key standardization issues of the 3GPP. This is a work for developing a 3GPP system to a system that supports various wireless access technologies based on an IP and the work has been progressed for the purpose of an optimized packet based system that minimizes a transmission delay with a further improved data transmission capability.
An SAE higher-level reference model defined in the 3GPP SA WG2 includes a non-roaming case and a roaming case of various scenarios, and a detailed content may be referred in TS 23.401 and TS 23.402 which are 3GPP standard documents.
FIG. 1 is a structural diagram of an evolved mobile communication network.
One of largest features of the network structure of FIG. 1 is based on a 2 tier model of eNodeB of an evolved UTRAN and a gateway of a core network and although accurately coincides with each other, the eNodeB 920 has functions of NodeB and RNC of an existing UMTS system and the gateway has an SGSN/GGSN function of the existing system.
Another key feature is that a control plane and a user plane between an access network and the core network are switched to different interfaces. In the existing UMTS system, one Iu interface exists between an RNC and an SGSN, while a mobility management entity (MME) 951 that undertakes processing of a control signal has a structure separated from a gateway (GW), and as a result, two interfaces of S1-MME and S1-U are respectively used. The GW includes a serving-gateway (hereinafter, referred to as ‘S-GW’) 952 and a packet data network gateway (hereinafter, referred to as ‘PDN-GW’ or ‘P-GW’) 953.
FIG. 2 is a diagram illustrating the relationship between (e)NodeB and Home (e)NodeB.
In the 3rd or 4th mobile communication system, an attempt to increase a cell capacity is continuously made in order to support a high-capacity service and a bidirectional service such as multimedia contents, streaming, and the like.
That is, as various large-capacity transmission technologies are required with development of communication and spread of multimedia technology, a method for increase a radio capacity includes a method of allocating more frequency resources, but there is a limit in allocating more frequency resources to a plurality of users with limited frequency resources.
An approach to use a high-frequency band and decrease a cell radius has been made in order to increase the cell capacity. When a cell having a small radius, such as a pico cell is adopted, a band higher than a frequency used in the existing cellular system may be used, and as a result, it is possible to transfer more information. However, since more base stations should be installed in the same area, higher cost is required.
In recent years, a femto base station such as a Home (e)NodeB 930 has been proposed while making the approach to increase the cell capacity by using the small cell.
The Home (e)Node 930 has been researched based on a RAN WG3 of the 3GPP Home (e)NodeB and in recent years, the Home (e)NodeB 30 has been in earnest researched even in an SA WG.
The (e)NodeB 920 illustrated in FIG. 2 corresponds to a macro base station and the Hoem (e)NodeB 930 illustrated in FIG. 2 may correspond to the femto base station. In the specification, (e)NodeB intends to be described based on terms of the 3GPP and (e)NodeB is used when NodeB and eNodeB are mentioned together. Further, Home (e)NodeB is used when Home NodeB and Home eNodeB are mentioned together.
The (e)NodeB 920 transmits and receives signals of the MME 951 and the control plane and transmits and receives signals of the S-GW 952 and the user plane. Similarly, the (e)NodeB 930 also transmits and receives signals of the MME 951 and the control plane and transmits and receives data of the S-GW 952 and the user plane. The PDN-GW 953 serves to transmit and receive the data from the S-GW 952 to an IP service network of a mobile communication provider.
Interfaces marked with dotted lines are used to transmit control signals among the (e)NodeB 920, the Home (e)NodeB 930, and then MME 951. In addition, interfaces marked with solid lines are used to transmit the data of the user plane.
FIG. 3 is an exemplary diagram illustrating a structure of a network including a Home Node and a Home (e)NodeB.
As illustrated in FIG. 3A, a core network 950 includes the MME 951, the serving gateway (S-GW) 952, an SGSN 956, and a packet data network gateway (P-GW) 953. Besides, the core network 950 may further include a PCRF 954 and an HSS 955.
FIG. 3A illustrates the Home NodeB 931 by a UMTS terrestrial radio access network (UTRAN) and the Home eNodeB 932 by an evolved-UTRAN (E-UTRAN). The Home NodeB 931 by the UTRAN is connected with the SGSN 956 through a gateway 935. The Home eNodeB 932 by the E-UTRAN is connected with the MME 951 and the S-GW 952. In this case, the control signal is transferred to the MME 951 and the user data signal is transferred to the S-GW 952. Further, the gateway 935 may be present between the Home eNodeB 932 by the E-UTRAN and the MME 951.
Meanwhile, referring to FIG. 3B, an interface of the Home eNodeB 932 by the E-UTRAN is illustrated. The Home eNodeB 932 by the E-UTRAN and the gateway 935 are called a Home eNodeB subsystem. The Home eNodeB 932 by the E-UTRAN is connected with a UE 910 through an LTE-Uu interface. The Home eNodeB 932 and the MME 951 are connected through an S1-MME interface. In addition, the Home eNodeB 932 and the S-GW 952 are connected through an S1-U interface. In this case, the S1-MME interface and the S1-U interface may pass through the gateway 935. The MME 951 and the S-GW 952 are connected through an S11 interface. In addition, the MME 951 and the HSS 955 are connected through an S6a interface.
FIG. 4 is an exemplary diagram illustrating an interface between he Home eNodeB and the MME illustrated in FIG. 3.
As illustrated in FIG. 4, each of the Home eNodeB 932 and the MME 951 includes a first layer (physical layer), a second layer (medium connection control layer), a third layer (Internet protocol (IP) layer), a signaling control transmission protocol (SCTP), and an S1 application protocol (S1-AP).
The S1-AP is an application layer protocol between the Home eNodeB 932 and the MME 951. The STCP assures transferring of a signaling message between the Home eNodeB 932 and the MME 951.
FIGS. 5a and 5b are general structural diagrams of an IP-connectivity access network (IP-CAN) that provides a short message.
Referring to FIG. 5a, an IP-short-message-gateway (IP-SM-GW) performs protocol interworking in order to transmit and receive a short message of an IP based terminal. That is, when the IP-SM-GW receives an SIP message including short message service associated information (for example, a mobile originated short message), a delivery report, and the like, the IP-SM-GW extracts and delivers the SMS associated information. In this case, a protocol used in communication between an MSC or an SGSN and an SMS-GMSC/SMS-IWMSC is applied under the existing GSM/UMTS environment. On the contrary, when the IP-SM-GW receives from the SMS-GMSC/SMS-IWMSC SMS associated information (for example, a mobile terminated short message, a submit report, and the like) toward the IP based terminal, the information contained in the SIP message is delivered to the IP based terminal. In this case, a protocol used in communication between an MSC or an SGSN and an SMS-GMSC/SMS-IWMSC is applied under the existing GSM/UMTS environment.
The SMS associated information is included in a transfer protocol data unit (TPDU) transferred through a short message transfer layer (SM-TL) of FIG. 5b and the TPDU is encapsulated in a relay protocol data unit transferred through a short message relay layer (SM-RL) to be transferred.